1. Field of the Invention
This invention relates to a ceramic material for an octal member, a production method thereof and a ceramic optical part, more particularly to a black and porous ceramic material which can be used in an octal part, a ceramic optical part and production methods thereof. The invention provides a novel ceramic material for an optical member, which is a ceramic material for an optical member constituted from a porous reaction-sintered sintered ceramic body that shows black, wherein it shows no variation regarding the accuracy of the sintered body, its reflectance at the visible light region is 20% or less, its surface is an unprocessed baked face and it can be suitably used as a high accuracy and high quality optical part, and provides new techniques and new product regarding ceramic optical parts.
2. Description of the Related Art
In a preceding reference, examples are reported for example on the use of a ceramic as an optical parts which has low thermal expansion and proper rigidity and abrasion resistance and shows black color, effected by Sposhmen or Cordierite (JP-A-2002-220277). Also, another preceding reference proposes a ceramic for optical members, which shows black color by containing, for example, Cordierite, as a base material, and carbon (JP-A-11-343168).
In addition, though not applications to optical members, there are reports on the inhibition of uneven color and the like at the time of sintering through the blackening of compact ceramics. However, in the case of compact ceramics, accuracy of the sintered body varies due to large shrinkage at the time of sintering, which results in the necessity to carry out a secondary processing and thereby poses a problem of increased cost or the like when, for example, this is used as an optical part for which high uniformity and high accuracy are required.